Photosensitive composition, photosensitive lithography plate and method for producing lithography plate

ABSTRACT

Disclosed is a light sensitive composition containing a compound A having a group capable of undergoing radical polymerization, a compound B having a group capable of undergoing cationic polymerization, a photopolymerization initiator C, and a polymer binder D, the light sensitive composition being characterized in that the photopolymerization initiator C comprises an iron-arene complex and a halogenated alkyl group-containing compound.

FIELD OF THE INVENTION

The present invention relates to a light sensitive composition, a lightsensitive planographic printing plate material and a manufacturingmethod of a printing plate, and particularly to a light sensitivecomposition, a light sensitive planographic printing plate material anda manufacturing method of a printing plate, providing high sensitivityand excellent printing durability.

BACKGROUND OF THE INVENTION

Generally, a negative working light sensitive planographic printingplate material is imagewise exposed to harden the exposed portions,dissolving away the unexposed portions, washed with water, and subjectedto finisher gumming treatment to obtain a planographic printing plate.In recent years, an attempt has been made in which after digitalexposure is made based on image information employing a laser light inorder to provide high dissolving power and sharpness, developmenttreatment is carried out to obtain a planographic printing plate. Forexample, there is a system for preparing a planographic printing plate,in which a light source is modulated based on image informationtransported from a communication line, or based on output signals froman electronic plate making system or an image processing system, a lightsensitive material is directly scanning exposed employing the lightsource.

There is a problem in a conventional planographic printing platematerial employing a diazo resin in that it is difficult to increasesensitivity or to carry out spectral sensitization for meeting anemission wavelength of a laser for digital exposure In order to obtainhigh sensitivity.

In recent years, as a light sensitive material suitable for laserexposure, which can increase sensitivity and carry out spectralsensitization, a planographic printing plate material has been notedwhich comprises a photopolymerizable light sensitive layer containing aphotopolymerization initiator. However, a planographic printing platematerial for CTP (Computer To Plate) for recording a digital imageaccording to laser-exposure is generally poor in printing durability. Aprinting plate material with high printing durability has been desiredin various printing industries such as newspaper printing or commercialprinting industries.

In order to obtain high sensitivity, a method of employing aphotopolymerization has been studied, and a method of employing ans-triazine compound as a photopolymerization initiator has been proposed(see, for example, Japanese Patent O.P.I. Publication Nos. 48-36281,54-74887, and 64-35548.). However, this method could not providesatisfactory sensitivity. Further, a technique of employing acombination of an iron-arene compound and a peroxide as aphotopolymerization initiator has been proposed (see, for example,Japanese Patent O.P.I. Publication No. 59-219307.). However, thistechnique also could not provide satisfactory sensitivity.

In order to obtain high printing durability, there have been disclosed atechnique employing a titanocene compound as a photopolymerizationinitiator (see Japanese Patent O.P.I. Publication Nos. 2001-209170 and2001-183822), a technique employing autoagglutination of urethane bondof a urethane resin (see Japanese Patent O.P.I. Publication No.2001-100412), a technique employing a an ethylenically unsaturatedcompound containing a phosphate ester bond (see Japanese Patent O.P.I.Publication No. 10-10719), and a technique employing a silane couplingagent or employing a diazonium compound disclosed in Japanese PatentO.P.I. Publication No. 2001-249444. These techniques are notsatisfactory, and a method solving the above problems has been desired.

Accordingly, an object of the invention is to provide a light sensitivecomposition, a light sensitive planographic printing plate material anda manufacturing method of a printing plate, providing high sensitivityand excellent printing durability.

DISCLOSURE OF THE INVENTION

The above object of the invention can be attained by one of thefollowing constitutions:

1. A light sensitive composition containing a compound A having a groupcapable of undergoing radical polymerization, a compound B having agroup capable of undergoing cationic polymerization, aphotopolymerization initiator C, and a polymer binder D, wherein thephotopolymerization initiator C comprises an iron-arene complex and ahalogenated alkyl group-containing compound.

2. The light sensitive composition of item 1 above, wherein thehalogenated alkyl group-containing compound is at least one selectedfrom the group consisting of a trichloromethyl group-containingcompound, a tribromomethyl group-containing compound, a dichloromethylgroup-containing compound, and a dibromomethyl group-containingcompound.

3. The light sensitive composition of item 1 or 2 above, wherein thecompound B having the group capable of undergoing cationicpolymerization further has a group capable of undergoing radicalpolymerization, the group capable of undergoing cationic polymerizationcomprising any one of an oxirane ring, an oxetane ring and a dioxolanering in the chemical structure.

4. The light sensitive composition of any one of items 1 through 3above, wherein the compound B is a compound represented by the followingformula (A):

wherein R¹ represents a hydrogen atom, or a methyl group; R² representsan alkyl group; and X¹ represents a single bond or a divalent organicgroup.

5. The light sensitive composition of any one of items 1 through 3above, wherein the compound B is at least one selected from the groupconsisting of a compound represented by the following formula (B) and acompound represented by the following formula (C):

wherein R³ represents a substituted or unsubstituted alkyl group, asubstituted or unsubstituted aryl group or a substituted orunsubstituted acyl group; R⁴ represents a hydrogen atom or an alkylgroup; and X² represents a single bond or a divalent organic group.

wherein R⁵ represents a substituted or unsubstituted alkyl group or asubstituted or unsubstituted aryl group; R⁶ represents a hydrogen atomor an alkyl group; and X³ represents a single bond or a divalent organicgroup.

6. A light sensitive planographic printing plate material comprising asupport having a hydrophilic surface, and coated on the hydrophilicsurface, the light sensitive composition of any one of items 1 through 5above.

7. A process of manufacturing a planographic printing plate, wherein theprocess comprises the step of imagewise exposing the light sensitiveplanographic printing plate material of item 6 above, employing a laseremitting light with a wavelength of from 350 to 450 nm to record animage.

8. A process of manufacturing a planographic printing plate, wherein theprocess comprises the step of imagewise exposing the light sensitiveplanographic printing plate material of item 7 above, employing a laseremitting light with a wavelength of from 470 to 550 nm to record animage.

PREFERRED EMBODIMENTS OF THE INVENTION

The preferred embodiments of the invention will be explained in detailbelow, but the invention is not limited thereto.

The present invention is characterised in that in a light sensitivecomposition containing a compound A having a group capable of undergoingradical polymerization, a compound B having a group capable ofundergoing cationic polymerization, a photopolymerization initiator C,and a polymer binder D, the photopolymerization initiator C comprises aniron-arene complex and a halogenated alkyl group-containing compound. Ithas been found that particularly in a light sensitive composition orlight sensitive planographic printing plate material which comprises, asa photopolymerization initiator, an iron-arene complex and a halogenatedalkyl group-containing compound, cationic polymerization and radicalpolymerization proceeds simultaneously, resulting in greatly improvedsensitivity, and printing durability, and the invention has been made.

The present invention will be further detailed below.

<<Compound Having a Group Capable of Undergoing Radical Polymerization>>

As the compound having a group capable of undergoing radicalpolymerization in the invention, there are a radical polymerizablemonomer, and a polyfunctional monomer or oligomer having two or more ofan ethylenic double bond in the molecule generally used in anultraviolet curable resin composition. The compounds are notspecifically limited.

Preferred examples thereof include a monofunctional acrylate such as2-ethylhexyl acrylate, 2-hydroxypropyl acrylate, glycerol acrylate,tetrahydrofurfuryl acrylate, phenoxyethyl acrylate, nonylphenoxyethylacrylate, tetrahydrofurfuryl-oxyethyl acrylate,tetrahydrofurfuryloxyhexanorideacrylate, an ester of1,3-dioxane-ε-caprolactone adduct with acrylic acid, or 1,3-dioxolaneacrylate; a methacrylate, itaconate, crotonate or maleate alternative ofthe above acrylate; a bifunctional acrylate such as ethyleneglycoldiacrylate, triethyleneglycol diacrylate, pentaerythritol diacrylate,hydroquinone diacrylate, resorcin diacrylate, hexanediol diacrylate,neopentyl glycol diacrylate, tripropylene glycol diacrylate,hydroxypivalic acid neopentyl glycol diacrylate, neopentyl glycoladipate diacrylate, diacrylate of hydroxypivalic acid neopentylglycol-s-caprolactone adduct,2-(2-hydroxy-1,1-dimethylethyl)-5-hydroxymethyl-5-ethyl-1,3-dioxanediacrylate, tricyclodecanedimethylol acrylate, tricyclodecanedimethylolacrylate-c-caprolactone adduct or 1,6-hexanediol diglycidyletherdiacrylate; a dimethacrylate, diitaconate, dicrotonate or dimaleatealternative of the above diacrylate; a polyfunctional acrylate such astrimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate,trimethylolethane triacrylate, pentaerythritol triacrylate,pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate,dipentaerythritol pentaacrylate, dipentaerythritol hexacrylate,dipentaerythritol hexacrylate-ε-caprolactone adduct, pyrrogalloltriacrylate, propionic acid dipentaerythritol triacrylate, propionicacid dipentaerythritol tetraacrylate or hydroxypivalylaldehyde modifieddimethylolpropane triacrylate; a methacrylate, itaconate, crotonate ormaleate alternative of the above polyfunctional acrylate.

A prepolymer can be used, and examples of the prepolymer includecompounds as described later. The prepolymer with a photopolymerizableproperty, which is obtained by incorporating acrylic acid or methacrylicin an oligomer with an appropriate molecular weight, can be suitablyemployed. These prepolymers can be used singly, in combination or astheir mixture with the above described monomers and/or oligomers.

Examples of the prepolymer include polyester (meth)acrylate obtained byincorporating (meth)acrylic acid in a polyester of a polybasic acid suchas adipic acid, trimellitic acid, maleic acid, phthalic acid,terephthalic acid, hymic acid, malonic acid, succinic acid, glutaricacid, itaconic acid, pyromellitic acid, fumalic acid, pimelic acid,sebatic acid, dodecanic acid or tetrahydrophthalic acid with a polyolsuch as ethylene glycol, ethylene glycol, diethylene glycol, propyleneoxide, 1,4-butane diol, triethylene glycol, tetraethylene glycol,polyethylene glycol, grycerin, trimethylol propane, pentaerythritol,sorbitol, 1,6-hexanediol or 1,2,6-hexanetriol; an epoxyacrylate such asbisphenol A•epichlorhydrin•(meth)acrylic acid or phenolnovolak•epichlorhydrin•(meth)acrylic acid obtained by incorporating(meth)acrylic acid in an epoxy resin; an urethaneacrylate such asethylene glycol•adipic acid•tolylenediisocyanate•2-hydroxyethylacrylate,polyethylene glycol•tolylenediisocyanate•2-hydroxyethylacrylate,hydroxyethylphthalyl methacrylate•xylenediisocyanate,1,2-polybutadieneglycol•tolylenediisocyanate-2-hydroxyethylacrylate ortrimethylolpropane•propyleneglycol•tolylenediisocyanate•2-hydroxyethylacrylate, obtained byincorporating (meth)acrylic acid in an urethane resin; a siliconeacrylate such as polysiloxane acrylate, orpolysiloxane•diisocyanate•2-hydroxyethylacrylate; an alkyd modifiedacrylate obtained by incorporating a methacroyl group in an oil modifiedalkyd resin; and a spiran resin acrylate.

The light sensitive composition of the invention may contain a monomersuch as a phosphazene monomer, triethylene glycol, an EO modifiedisocyanuric acid diacrylate, an EO modified isocyanuric acidtriacrylate, dimethyloltricyclodecane diacrylate, trimethylolpropaneacrylate benzoate, an alkylene glycol acrylate, or a urethane modifiedacrylate, or an addition polymerizable oligomer or prepolymer having astructural unit derived from the above monomer.

The ethylenic monomer used in the invention is preferably a phosphatecompound having at least one (meth)acryloyl group. The phosphatecompound is a compound having a (meth)acryloyl group in which at leastone hydroxyl group of phosphoric acid is esterified, and the phosphatecompound is not limited as long as it has a (meth)acryloyl group.

In the invention, a reaction product of a polyhydric alcohol having atertiary amino group in the molecule, a diisocyanate and a compoundhaving a hydroxyl group and an addition polymerizable ethylenicallydouble bond in the molecule is preferably used. Examples of thepolyhydric alcohol having a tertiary amino group in the molecule includetriethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine,N-ethyldiethanolamine, N-n-butyldiethanolamine,N-tert-butyldiethanolamine, N,N-di(hydroxyethyl)aniline, N,N, N′,N′-tetra-2-hydroxypropylethylenediamine, p-tolyldiethanolamine, N,N, N′,N′-tetra-2-hydroxyethylethylenediamine, N,N-bis(2-hydroxypropyl)aniline,allyldiethanolamine, 3-dimethylamino-1,2-propane diol,3-diethylamino-1,2-propane diol, N,N-di(n-propylamino)-2,3-propane diol,N,N-di(iso-propylamino)-2,3-propane diol, and3-(N-methyl-N-benzylamino)-1,2-propane diol, but the invention is notspecifically limited thereto.

Examples of the diisocyanate include butane-1,4-diisocyanate,hexane-1,6-diisocyanate, 2-methylpentane-1,5-diisocyanate,octane-1,8-diisocyanate, 1,3-diisocyanatomethylcyclohexanone,2,2,4-trimethylhexane-1,6-diisocyanate, isophorone diisocyanate,1,2-phenylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylenediisocyanate, tolylene-2,4-diisocyanate, tolylene-2,5-diisocyanate,tolylene-2,6-diisocyanate, 1,3-di(isocyanatomethyl)benzene, and1,3-bis(1-isocyanato-1-methylethyl)benzene, but the invention is notspecifically limited thereto. Examples of the compound having a hydroxylgroup and an addition polymerizable ethylenically double bond in themolecule include the-following compounds MH-1 through MH-13, but theinvention is not specifically limited thereto. Preferred examplesthereof include 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate,4-hydroxybutyl acrylate, 2-hydroxypropylene-1,3-dimethacrylate, and2-hydroxypropylene-1-methacrylate-3-acrylate.

The reaction product above can be synthesized according to the samemethod as a conventional method in which a urethaneacrylate compound isordinarily'synthesized employing an ordinary diol, a diisocyanate and anacrylate having a hydroxyl group.

Besides the above compounds, compounds disclosed in Japanese PatentO.P.I. Publication Nos. 58-212994, 61-6649, 62-46688, 62-48589,62-173295, 62-187092, 63-67189, and 1-244891, compounds described onpages 286 to 294 of “11290 Chemical Compounds” edited by KagakukogyoNipposha, and compounds described on pages 11 to 65 of “UV•EB KokaHandbook (Materials)” edited by Kobunshi Kankokai can be suitably used.Of these compounds, compounds having two or more acryl or methacrylgroups in the molecule are preferable, and those having a molecularweight of not more than 10,000, and preferably not more than 5,000 aremore preferable.

The content of the compound having a group capable of undergoing radicalpolymerization in the light sensitive composition is-preferably from 10to 70% by weight, and more preferably from 20 to 60% by weight, based onthe solid component of the composition.

<<Compound Having a Group Capable of Undergoing CationicPolymerization>>

In the invention, as the group capable of undergoing cationicpolymerization, there are a group having a cyclic ether structure suchas an oxirane ring, an oxetane ring or a dioxolane ring; and a grouphaving an unsaturated ether structure such as vinyl ether or allylether.

Preferred is a compound having an oxirane ring, an oxatane ring or adioxalane ring, as the group capable of undergoing cationicpolymerization, and a group capable of undergoing radicalpolymerization. A compound represented by formula (A) above isespecially preferred, which has an acryloyl group or a methacryloylgroup in the molecule. A compound represented by formula (B) or (C)above is also especially preferred.

Examples of these compounds will be listed below, but the invention isnot limited thereto.

As the compound having a group capable of undergoing cationicpolymerization in the invention, there is an oxetane compound having anoxetane ring. In the invention, as the oxetane compound, an oxetanecompound having 1 to 4 oxetane rings is preferably employed. An oxetanecompound having five or more oxetane rings provides a composition withless fluidity, which may not be applied to printing. Any oxetanecompound can be used, as long as it is an oxetane compound having 1 to 4oxetane rings.

As one example of an oxetane compound having one oxetane ring, anoxetane compound represented by the following formula (1) is cited.

In formula (1), R¹ represents a hydrogen atom, an alkyl group havingfrom 1 to 6 carbon atoms such as a methyl group, an ethyl group, apropyl group, a butyl group, etc.; a fluoroalkyl group having from 1 to6 carbon atoms; an allyl group; an aryl group; a furyl group; or athienyl group; and R² represents an alkyl group having from 1 to 6carbon atoms such as a methyl group, an ethyl group, a propyl group, abutyl group, etc.; an alkenyl group having from 2 to 6 carbon atoms suchas a 1-propenyl group, a 2-propenyl group, a 2-methyl-1-propenyl group,a 2-methyl-2-propenyl group, a 1-butenyl group, a 2-butenyl group, a3-butenyl group, etc.), an aromatic ring-containing group such as aphenyl group, a benzyl group, a fluorobenzyl group, a methoxybenzylgroup; a phenoxyethyl group, etc.; an alkylcarbonyl group having from 2to 6 carbon atoms such as an ethylcarbonyl group, a propylcarbonylgroup, a-butylcarbonyl group, etc.; an alkoxycarbonyl group having from2 to 6 carbon carbons such as an ethoxycarbonyl group, a propoxycarbonylgroup, a butoxycarbonyl group, etc.; an N-alkylcarbamoyl group havingfrom 2 to 6 carbon atoms such as an ethylcarbamoyl group, apropylcarbamoyl group, a butylcarbamoyl group, a pentylcarbamoyl, etc.

As one example of an oxetane compound having two oxetane rings, anoxetane compound represented by the following formula (2) is cited.

In formula (2), R¹ represents the same group as those denoted in R₁ informula 1; and R³ represents a straight chained or branched alkylenegroup such as an ethylene group, a propylene group, a butylene group,etc.; a straight chained or branched polyalkyleneoxy group such as apoly(ethyleneoxy) group, a poly(propyleneoxy group, etc.; a straightchained or branched unsaturated divalent hydrocarbon group such apropenylene group, a methylpropenylene group, a butenylene group, etc.;an alkylene group containing a carbonyl group; an alkylene groupcontaining a carbonyloxy group; or an alkylene group containing acarbamoyl group. R³ also represents a divalent group selected fromgroups represented by the following formulae (3), (4), and (5).

In formula (3), R⁴ represents a hydrogen atom, an alkyl group havingfrom 1 to 4 carbon atoms such as a methyl group, an ethyl group, apropyl group, a butyl group, etc.; an alkoxy group having from 1 to 4carbon atoms such as a methoxy group, an ethoxy group, a propoxy group,a butoxy group, etc.; a halogen atom such as a chlorine atom, a bromineatom, etc.; a nitro group; a cyano group; a mercapto group; a loweralkylcarboxy group; carboxyl group; or a carbamoyl group.

In formula (4), R⁵ represents an oxygen atom, a sulfur atom, a methylenegroup, —NH—, —SO—, —SO₂—, —(CF₃)₂—, or —C(CH₃)₂—.

In formula (11), R⁶ represents an alkyl group having from 1 to 4 carbonatoms such as a methyl group, an ethyl group, a propyl group, a butylgroup, etc., or an aryl group; “n” represents an integer of from 0 to2000; and R⁷ represents an alkyl group having from 1 to 4 carbon atomssuch as a methyl group, an ethyl group, a propyl group, a butyl group,etc, or an aryl group, or a group represented by the following formula(6).

In formula (6), R⁸ represents an alkyl group having from 1 to 4-carbonatoms such as a methyl group, an ethyl group, a propyl group, a butylgroup, etc., or an aryl group; and m represents an integer of from 0 to100.

Examples of a compound having two oxetane rings include the followingexemplified compounds 1 and 2.

Exemplified compound 1 is a compound in which in formula (2), R¹ is anethyl group, and R³ is a carbonyl group. Exemplified compound 2 is acompound in which in formula (2), R¹ is an ethyl group, and R³ is agroup in which in formula (5), R⁶ is a methyl group, R⁷ is a methylgroup, and n is 1.

As another example of an oxetane compound having two oxetane rings, anoxetane compound represented by the following formula (7) is cited.

As an example of an oxetane compound having three or four oxetane rings,an oxetane compound represented by the following formula (8) is cited.

In formula (8), R¹ is the same as those denoted in R¹ of formula (1);and R⁹ represents a branched alkylene group having 1 to 12 carbon atomssuch as a group represented by A, B, or C below, a branchedpolyalkyleneoxy group such as a group represented by D below, or abranched alkylene group containing a silylether group such as a grouprepresented by E below. “j” represents an integer of 3 or 4.

In formula A, R¹⁰ represents a lower alkyl group such as a methyl group,an ethyl group, or a propyl group. In formula D, p represents an integerof from 1 to 10.

As an example of an oxetane compound having three to four oxetane rings,an exemplified compound 3 is cited.

As a compound having 1 to 4 oxetane rings other than the compoundsdescribed above, a compound represented by the following formula (9) iscited.

In formula (9), R⁸ is the same as those denoted in R⁸ of formula (6);R¹¹ represents an alkyl group having 1 to 4 carbon atoms such as amethyl group, an ethyl group, or a propyl group, or a trialkylsilylgroup; r represents an integer of from 1 to 4. R1 is the same as thosedenoted in formula (1) above.

The preferred oxetane compounds used in the invention are exemplifiedcompounds as shown below.

Besides the above-described oxetane compounds, polymeric oxetanecompounds having 1 to 4 oxetane rings with a molecular weight of 1000 to5000 can be used. Examples thereof include the following compounds.

In the above, p is from 20 to 200.

As another compound having a group capable of undergoing cationicpolymerization, there are a compound having an epoxy group and acompound having a vinyl ether group. As the compound having an epoxygroup, various compounds can be used. Examples of an epoxy compoundhaving one epoxy group include phenyl glycidyl ether and butyl glycidylether. Examples of an epoxy compound having two or more epoxy groupsinclude hexane diol diglycidyl ether, tetraethylene glycol diglycidylether, trimethylolpropane triglycidyl ether, bisphenol A diglycidylether, and epoxidated novolak resin. In the invention, an alicyclicepoxy compound is especially preferred. Examples thereof will be listedbelow.

A light sensitive composition containing the epoxy compound and theoxetane compound having one to four oxetane rings can further increasethe curing speed of the composition. The epoxy compound content of thelight sensitive composition is preferably from 5 to 95 parts by weight,based on 100 parts by weight of the total content of the epoxy compoundand the oxetane compound having one to four oxetane rings.

As the compound having a vinyl ether group, various compounds can beused. Examples of a compound having one vinyl ether group includehydroxyethyl vinyl ether, hydroxybutyl vinyl ether, propenyl etherpropylene carbonate, and cyclohexyl vinyl ether. Examples of a compoundhaving two or more vinyl ether groups include cyclohexane dimethanoldivinyl ether, triethylene glycol divinyl ether, and novolak resindivinyl ether.

A light sensitive composition containing the compound having a vinylether group and the oxetane compound having one to four oxetane ringscan further increase the curing speed.

The content of the compound having a vinyl ether group in the lightsensitive composition is preferably from 5 to 95 parts by weight, basedon 100 parts by weight of the total content of the compound having avinyl ether group and the oxetane compound having one to four oxetanerings.

The content of the compound B) capable of undergoing cationicpolymerization in the light sensitive composition is preferably from 2to 50% by weight, and more preferably from 5 to 30% by weight, based onthe solid component of the composition.

<<Photopolymerization Initiator>>

The chemical structure of an iron-arene complex in the invention isrepresented by formula (D) below: Formula (D)[A-Fe—B]⁺X⁻wherein A represents a cyclopentadienyl group or an alkyl-substitutedcyclopentadienyl group; B represents arene; and X⁻ represents an anionicgroup.

Examples of the arene include benzene, toluene, xylene, cumene,naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, and fluorene.Examples of the X⁻ include PF₆ ⁻, BF₄ ⁻, SbF₆ ⁻, AlF₄ ⁻, and CF₃SO₃ ⁻.Preferred examples of the iron-arene complex will be listed below, butthe invention is not limited thereto.

A halogenated alkyl group-containing compound in the invention ispreferably a polyhalide compound. Examples of the polyhalide compoundinclude a polyhalogen-containing acetophenone such astribromoacetophenone, trichloroacetophenone,o-nitro-tribromoacetophenone, p-nitro-tribromoacetophenone,m-nitro-tribromoacetophenone, m-bromo-tribromoacetophenone, orp-bromo-tribromoacetophenone; a polyhalogen-containing sulfoxide such asbis(tribromomethyl) sulfoxide, dibromomethyl-tribromomethyl sulfoxide; apolyhalogen-containing sulfone such as bis(tribromomethyl) sulfone,trichloromethyl-phenylsulfone, tribromomethyl-phenylsulfone,trichloromethyl-p-chlorophenylsulfone,tribromomethyl-p-nitrophenylsulfone,2-trichloromethyl-benzothiazolesulfone, or2,4-dichlorophenyl-trichloromethylsulfone; a polyhalogen-containingpyrron compound; a polyhalogen-containing triazine compound; and apolyhalogen-containing oxadiazole compound.

Preferred examples of the polyhalogen compound will be listed below, butthe invention is not limited thereto.

The content of the photopolymerization initiator C) in the lightsensitive composition is preferably from 1 to 30% by weight, and morepreferably from 2 to 15% by weight, based on the solid component of thecomposition. The epoxy compound content ratio (by weight) of theiron-arene complex to the halogenated alkyl group-containing compound inthe light sensitive composition is preferably from 5:95 to 95:5, andmore preferably from 20:80 to 80:20.

<<Polymer Binder>>

Next, a polymer binder will be explained.

As the polymer binder in the invention can be used a polyacrylate resin,a polyvinylbutyral resin, a polyurethane resin, a polyamide resin, apolyester resin, an epoxy resin, a phenol resin, a polycarbonate resin,a polyvinyl butyral resin, a polyvinyl formal resin, a shellac resin, oranother natural resin. These resins can be used as an admixture of twoor more thereof.

The polymer binder used in the invention is preferably a vinyl copolymerobtained by copolymerization of an acryl monomer, and more preferably acopolymer containing (a) a carboxyl group-containing monomer unit and(b) an alkyl methacrylate or alkyl acrylate unit as the copolymerizationcomponent.

Examples of the carboxyl group-containing monomer include anα,β-unsaturated carboxylic acid, for example, acrylic acid, methacrylicacid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydrideor a carboxylic acid such as a half ester of phthalic acid with2-hydroxymethacrylic acid.

Examples of the alkyl methacrylate or alkyl acrylate include anunsubstituted alkyl ester such as methylmethacrylate, ethylmethacrylate,propylmethacrylate, butylmethacrylate, amylmethacrylate,hexylmethacrylate, heptylmethacrylate, octylmethacrylate,nonylmethacrylate, decylmethacrylate, undecylmethacrylate,dodecylmethacrylate, methylacrylate, ethylacrylate, propylacrylate,butylacrylate, amylacrylate, hexylacrylate, heptylacrylate,octylacrylate, nonylacrylate, decylacrylate, undecylacrylate, ordodecylacrylate; a cyclic alkyl ester such as cyclohexyl methacrylate orcyclohexyl acrylate; and a substituted alkyl ester such as benzylmethacrylate, 2-chloroethyl methacrylate, N,N-dimethylaminoethylmethacrylate, glycidyl methacrylate, benzyl acrylate, 2-chloroethylacrylate, N,N-dimethylaminoethyl acrylate or glycidyl acrylate.

The polymer binder in the invention can further contain, as anothermonomer unit, a monomer unit derived from the monomer described in thefollowing items (1) through (14):

(1) A monomer having an aromatic hydroxy group, for example, o-, (p- orm-) hydroxystyrene, or o-, (p- or m-) hydroxyphenylacrylate;

(2) A monomer having an aliphatic hydroxy group, for example,2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,N-methylolacrylamide, N-methylolmethacrylamide, 4-hydroxybutyl acrylate,4-hydroxybutyl methacrylate, 5-hydroxypentyl acrylate, 5-hydroxypentylmethacrylate, 6-hydroxyhexyl acrylate, 6-hydroxyhexyl methacrylate,N-(2-hydroxyethyl)acrylamide, N-(2-hydroxyethyl)methacrylamide, orhydroxyethyl vinyl ether;

(3) A monomer having an aminosulfonyl group, for example, m- orp-aminosulfonylphenyl methacrylate, m- or p-aminosulfonylphenylacrylate, N-(p-aminosulfonylphenyl) methacrylamide, orN-(p-aminosulfonylphenyl)acrylamide;

(4) A monomer having a sulfonamido group, for example,N-(p-toluenesulfonyl)acrylamide, orN-(p-toluenesulfonyl)-methacrylamide;

(5) An acrylamide or methacrylamide, for example, acrylamide,methacrylamide, N-ethylacrylamide, N-hexylacrylamide,N-cyclohexylacrylamide, N-phenylacrylamide, N-nitrophenylacrylamide,N-ethyl-N-phenylacrylamide, N-4-hydroxyphenylacrylamide, orN-4-hydroxyphenylmethacrylamide;

(6) A monomer having a fluorinated alkyl group, for example,trifluoromethyl acrylate, trifluoromethyl methacrylate,tetrafluoropropyl methacrylate, hexafluoropropyl methacrylate,octafluoropentyl acrylate, octafluoropentyl methacrylate,heptadecafluorodecyl methacrylate, heptadecafluorodecyl methacrylate, orN-butyl-N-(2-acryloxyethyl)heptadecafluorooctylsulfonamide;

(7) A vinyl ether, for example, ethyl vinyl ether, 2-chloroethyl vinylether, propyl vinyl ether, butyl vinyl ether, octyl vinyl ether, orphenyl vinyl ether;

(8) A vinyl ester, for example, vinyl acetate, vinyl chroloacetate,vinyl butyrate, or vinyl benzoate;

(9) A styrene, for example, styrene, methylstyrene, orchloromethystyrene;

(10) A vinyl ketone, for example, methyl vinyl ketone, ethyl vinylketone, propyl vinyl ketone, or phenyl vinyl ketone;

(11) An olefin, for example, ethylene, propylene, isobutylene,butadiene, or isoprene;

(12) N-vinylpyrrolidone, N-vinylcarbazole, or N-vinylpyridine,

(13) A monomer having a cyano group, for example, acrylonitrile,methacrylonitrile, 2-pentenenitrile, 2-methyl-3-butene nitrile,2-cyanoethyl acrylate, or o-, m- or p-cyanostyrene;

(14) A monomer having an amino group, for example, N,N-diethylaminoethylmethacrylate, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethylmethacrylate, polybutadiene urethane acrylate, N,N-dimethylaminopropylacrylamide, N,N-dimethylacrylamide, acryloylmorpholine,N-isopropylacrylamide, or N,N-diethylacrylamide.

Further another monomer may be copolymerized with the above monomer.

As the polymer binder is also preferred an unsaturated bond-containingcopolymer which is obtained by reacting a carboxyl group contained inthe above vinyl copolymer molecule with for example, a compound having a(meth)acryloyl group and an epoxy group. Examples of the compound havinga double bond and an epoxy group in the molecule include glycidylacrylate, glycidyl methacrylate and an epoxy group-containingunsaturated compound disclosed in Japanese Patent O.P.I. Publication No.11-27196.

The weight average molecular weight of the above copolymer is preferably10,000 to 200,000 measured by gel permeation chromatography (GPC), butis not limited thereto.

Anther polymer binder such as a polyvinylbutyral resin, a polyurethaneresin, a polyamide resin, a polyester resin, an epoxy resin, a novolakresin, or natural resin can be used together with the above vinylcopolymer, if necessary.

The content of the polymer binder in the light sensitive composition ofthe invention is preferably from 10 to 90% by weight, more preferablyfrom 15 to 70% by weight, and still more preferably from 20 to 60% byweight, based on the solid components of the composition, in view ofsensitivity.

The content of the vinyl copolymer in the light sensitive composition ofthe invention is preferably from 50 to 1000% by weight, and morepreferably from 80 to 100% by weight, based on the polymer binder used.

The acid value of the polymer binder is preferably from 10 to 150, morepreferably from 30 to 120, and still more preferably from 50 to 90, inview of balance of polarity of the photopolymerizable light sensitivelayer, which can prevent coagulation of pigment used in thephotopolymerizable light sensitive layer coating liquid.

(Sensitizing Dye)

When laser is used as a light source, the light sensitive layer in theinvention preferably contains a sensitizing dye. A dye having absorptionmaximum approximate to the emission wavelength of light of the lightsource is preferred.

Examples of dyes capable of sensitizing to visible to near infraredwavelength regions include cyanine, phthalocyanine, merocyanine, oxonol,porphyrin, a spiro compound, ferrocene, fluorene, fulgide, imidazole,perylene, phenazine, phenothiazine, polyene, an azo compound,diphenylmethane, triphenylmethane, polymethine acridine, cumarin,cumarin derivatives, ketocumarin, quinacridone, indigo, styryl, pyryliumcompounds, pyrromethene compounds, pyrazolotriazole compounds,benzothiazole compounds, barbituric acid derivatives, thiobarbituricacid derivatives, ketoalcohol borate complexes, and compound disclosedin EP 568,993, U.S. Pat. Nos. 4,508,811 and 5,227,277, andJapanese-Patent O.P.I. Publication Nos. 2001-125255 and 11-271969. Amongthese, dyes having a skeleton of cumarin, ketocumarin, oxonol,barbituric acid, pyrromethene borate or diphenylmethane are preferred.

Dyes having absorption maximum in the wavelength range of from 350 to600 nm, providing desired effects in the composition containing theiron-arene complex and the polyhalogen compound, include xanthenes,acridines, coumarins, and barbituric acid derivatives. A dye representedby formula (10) below is preferred.

In formula (10), A¹ and A² independently represent a carbon atom or ahetero atom; Q¹ represents a non-metallic atomic-group necessary to forma heterocyclic ring together with A¹ and A²; R¹ and R² independentlyrepresent a hydrogen atom, an alkyl group or an aryl group, providedthat R¹ and R² may combine with each other to form a ring; X¹ and X²independently represent a cyano group or a substituted carbonyl group,provided that X¹ and X² may combine with each other to form a ring; andn is an integer of from 0 to 2.

Examples of the sensitizing dye represented by formula (10) will belisted below, but the invention is not limited thereto. Sensitizing dyeNo.

(R¹ = R² = H) n 1

1 2

1 3

1 4

1 5

1 6

1 7

2 8

1 9

1 10

1

As other examples of the dye represented by formula (10), there arethose disclosed in Japanese Patent O.P.I. Publication No. 9-328505.

As a dye having absorption maximum in the wavelength range of from 350to 600 nm, providing more desired effects in the composition containingthe iron-arene complex and the polyhalogen compound, there is a dyerepresented by the following formula (11) or (12).

In formula (11), R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹² R¹³, R¹⁴ andR¹⁵ independently represent a hydrogen atom, an alkyl group, an alkoxygroup, an aryl group, a cyano group, a carboxyl group, or analkyloxycarbonyl group; and Z¹ represents an aryl group, a heterocyclicgroup, or —COR¹⁶ (in which R¹⁶ represents an alkyl group, an alkoxygroup, an aryl group, an aryloxy group or a heterocyclic group).

Examples of the sensitizing dye represented by formula (11) will belisted below, but the invention is not limited thereto.

In formula (12), R¹⁷, R¹⁸, R¹⁹, R²⁰, R²¹, R²², R²³, R²⁴, and R²⁵independently represent a hydrogen atom, an alkyl group, an alkoxygroup, an aryl group, a cyano group, a carboxyl group, or analkyloxycarbonyl group; and Z² represents an aryl group, a heterocyclicgroup, or —COR²⁶ (in which R¹⁶ represents an alkyl group, an alkoxygroup, an aryl group, an aryloxy group or a heterocyclic group).

Examples of the sensitizing dye represented by formula (12) will belisted below, but the invention is not limited thereto.

As a dye having absorption maximum in the wavelength range of from 350to 600 nm, providing more desired effects in the composition containingthe iron-arene complex and the polyhalogen compound, there are xanthenedyes such as rose Bengal, Phloxine, erythrosine, eosine andfluoresceine; coumarin dyes; and anthracene dyes.

Examples of these dyes will be listed below, but the invention is notlimited thereto.

As a dye having absorption maximum in the wavelength range of from 350to 600 nm, providing more desired effects in the composition containingthe iron-arene complex and the polyhalogen compound or in thecomposition containing the polyhalogen compound, dyes disclosed inJapanese Patent O.P.I. Publication Nos. 2000-98605, 2000-147763,2000-206690, 2000-258910, 2001-42524, and 2001-100412 are preferred.

A compound represented by formula (13) is more preferred.

In formula (13), R¹⁴ represents a hydrogen atom, a substituted orunsubstituted alkyl group, a substituted or unsubstituted alkenyl group,a substituted or unsubstituted aryl group, or a substituted orunsubstituted heterocyclic group; R¹⁵ and R¹⁶ combine with each other toform a ring; and X¹¹ and X¹² independently represent —CR¹⁷R¹⁸—, —O—,—S—, or —NR¹⁹—, in which R¹⁷, R¹⁸, and R¹⁹ independently represent ahydrogen atom, a substituted or unsubstituted alkyl group, a substitutedor unsubstituted alkenyl group, a substituted or unsubstituted arylgroup, or a substituted or unsubstituted heterocyclic group.

Examples of the alkyl group represented by R¹⁴ include a methyl group,an ethyl group, a propyl group, a butyl group, a hexyl group, an octylgroup, a decyl group, a dodecyl group, an isopropyl group, an isobutylgroup, an isopentyl group, a tert-butyl group or a 2-ethylhexyl group.Examples of the alkenyl group represented by R¹⁴ include a vinyl-group,a 2-propenyl group, or a 3-butenyl group, a 1-methyl-3-propenyl group,3-pentenyl group, a 1-methyl-3-butenyl group or a 4-hexenyl group.Examples of the aryl group represented by R¹⁴ include a phenyl group ora naphthyl group. Examples of the heterocyclic group represented by R¹⁴include heterocyclic groups derived from 5- or 6-membered heterocyclicrings such as a pyrrole ring, an imidazole ring, a pyrazole ring, anoxazole ring, a thiazole ring, an oxadiazole ring, a thiadiazole ring, abenzimidazole ring, a pyridine ring, a furan ring, a thiophene ring, acoumarone ring, a coumarin ring, a pyrrolidone ring, a piperidine ring,a morpholine ring, a sulfolane ring, a tetrahydrofuran ring, andtetrahydropyrane.

Examples of the substituted or unsubstituted alkyl group, thesubstituted or unsubstituted alkenyl group the substituted orunsubstituted aryl group or the substituted or unsubstitutedheterocyclic group represented by R¹⁷, R¹⁸, or R¹⁹ include the same asthose denoted in R¹⁴ above.

Examples of the sensitizing dye represented by formula (13) will belisted below, but the invention is not limited thereto.

The spectral sensitizing dye represented by formula (13) can be preparedaccording to conventional synthetic methods well known in the art.

The maximum absorption of the spectral sensitizing dye is determinedfrom the visible light absorption spectra of the dye, which is obtainedmeasurement of an acetonitrile solution of the dye at ordinarytemperature. When the dye is insoluble in acetonitrile, a due solution,in which the dye is dissolved in alcohols, 2-butanoe or water, isemployed.

In the invention, the spectral sensitizing dye is dissolved in a solventsuch as water or an organic solvent to obtain a dye solution, and thedye solution is added to the light sensitive composition. Examples ofthe organic solvent include alcohols such as methanol, ethanol, propanolor butanol, ketones such as acetone, methyl ethyl ketone, orcyclohexanone, aromatic hydrocarbons such as benzene, toluene, orxylene, glycols such as ethylene glycol, propylene glycol, or hexyleneglycol, glycol ethers such as ethyl cellosolve, butyl cellosolve, ethylcarbitol, butyl carbitol, diethyl cellosolve, or diethyl carbitol,N-methyl pyrrolidone, and dimethylformamide. The organic solvents can beused singly or in combination of two or more kinds thereof.

The content of the spectral sensitizing dye in the in the lightsensitive composition is not specifically limited, but is preferablyfrom 0.1 to 10 parts by weight, and more preferably from 0.5 to 5 partsby weight, based on 100 parts of the solid components of the lightsensitive composition. The content ratio of the photopolymerizationinitiator to the sensitizing dye in the light sensitive composition ispreferably from 1:100 to 100:1 by mole.

Next, various additives which can be added to the light sensitivecomposition, a support or a protective layer for a light sensitiveplanographic printing plate material, a method of coating the lightsensitive composition on the support, and an image formation methodemploying the light sensitive planographic printing plate material willbe explained.

(Various Additives)

The photopolymerizable light sensitive layer comprising the lightsensitive composition in the invention is preferably added with apolymerization inhibitor, in order to prevent undesired polymerizationof the ethylenically unsaturated monomer during the manufacture or afterstorage of the light sensitive planographic printing plate material.

Examples of the polymerization inhibitor include hydroquinone,p-methoxyphenol, di-t-butyl-p-cresol, pyrrogallol, t-butylcatechol,benzoquinone, 4,4′-thiobis (3-methyl-6-t-butylphenol), 2,2′-methylenebis(4-methyl-6-t-butylphenol), N-nitrosophenylhydroxylamine cerous salt,and 2-t-butyl-6-(3-t-butyl-6-hydroxy-5-mrthylbenzyl)-4-methylphenylacrylate.

The polymerization inhibitor content is preferably 0.01 to 5% by weightbased on the total solid content of the light sensitive layer. Further,in order to prevent undesired polymerization induced by oxygen, behenicacid or a higher fatty acid derivative such as behenic amide may beadded to the layer. After the light sensitive layer is coated layer, thecoated layer may be dried so that the higher fatty acid derivative islocalized at the vicinity of the surface of the light sensitive layer.The content of the higher fatty acid derivative is preferably 0.5 to 10%by weight, based on the total solid content of the light sensitivelayer.

A colorant can be also used. As the colorant can be used known materialsincluding commercially available materials. Examples of the colorantinclude those described in revised edition “Ganryo Binran”, edited byNippon Ganryo Gijutu Kyoukai (publishe by Seibunndou Sinkosha), or“Color Index Binran”. Pigment is preferred.

Kinds of the pigment include black pigment, yellow pigment, red pigment,brown pigment, violet pigment, blue pigment, green pigment, fluorescentpigment, and metal powder pigment. Examples of the pigment includeinorganic pigment (such as titanium dioxide, carbon black, graphite,zinc oxide, Prussian blue, cadmium sulfide, iron oxide, or chromate oflead, zinc, barium or calcium); and organic pigment (such as azopigment, thioindigo pigment, anthraquinone pigment, anthanthronepigment, triphenedioxazine pigment, vat dye pigment, phthalocyaninepigment or its derivative, or quinacridone pigment).

Among these pigment, pigment is preferably used which does notsubstantially have absorption in the absorption wavelength regions of aspectral sensitizing dye used according to a laser for exposure. Theabsorption of the pigment used is not more than 0.05, obtained from thereflection spectrum of the pigment measured employing an integratingsphere and employing light with the wavelength of the laser used. Thepigment content is preferably 0.1 to 10% by weight, and more preferably0.2 to 5% by weight, based on the total solid content of thephotopolymerizable light sensitive layer composition.

When an argon laser (488 nm) or an SHG-YAG laser (532 nm) is used as alight source for exposure, violet pigment or blue pigment is preferablyused in view of the above absorption wavelength relationship or imagevisibility after development. Such pigment examples include Cobalt Blue,cerulean blue, alkali blue lake, Victria Blue lake, metal freephthalocyanine, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue,indigo, dioxane violet, isoviolanthrone violet, Indanthrone Blue, andIndanthrene BC. Among these, Phthalocyanine Blue and dioxane violet arepreferred.

A surfactant may be added to the layer in order to improve coatabilityof the layer. A preferred surfactant is a fluorine-contained surfactant.

Further, in order to improve physical properties of the cured lightsensitive layer, the layer can contain an inorganic filler or aplasticizer such as dioctyl phthalate, dimethyl phthalate or tricresylphosphate. The content of such a material is preferably not more than10% by weight, based on the total solid content of the light sensitivelayer.

The solvents used in the preparation of the coating liquid for thephotopolymerizable light sensitive layer in the invention include analcohol such as sec-butanol, isobutanol, n-hexanol, or benzyl alcohol; apolyhydric alcohol such as diethylene glycol, triethylene glycol,tetraethylene glycol, or 1,5-pentanediol; an ether such as propyleneglycol monobutyl ether, dipropylene glycol monomethyl ether, ortripropylene glycol monomethyl ether; a ketone or aldehyde such asdiacetone alcohol, cyclohexanone, or methyl cyclohexanone; and an estersuch as ethyl lactate, butyl lactate, diethyl oxalate, or methylbenzoate.

(Protective Layer or Oxygen Shielding Layer)

(Protective Layer: Oxygen Shielding Layer)

In the invention, a protective layer is preferably provided on thephotopolymerizable light sensitive layer. It is preferred that theprotective layer (oxygen shielding layer) is highly soluble in thedeveloper as described above (generally an alkaline solution). Polyvinylalcohol or polyvinyl pyrrolidone is preferably used in the protectivelayer. Polyvinyl alcohol has the effect of preventing oxygen fromtransmitting and polyvinyl pyrrolidone has the effect of increasingadhesion between the oxygen shielding layer and the photopolymerizablelight sensitive layer adjacent thereto.

Besides the above two polymers, the oxygen shielding layer may contain awater soluble polymer such as polysaccharide, polyethylene glycol,gelatin, glue, casein, hydroxyethyl cellulose, carboxymethyl cellulose,methyl cellulose, hydroxyethyl starch, gum arabic, sucrose octacetate,ammonium alginate, sodium alginate, polyvinyl amine, polyethylene oxide,polystyrene sulfonic acid, polyacrylic acid, or a water solublepolyamide.

In the light sensitive planographic printing plate material in theinvention, adhesive strength between the protective layer and thephotopolymerizable light sensitive layer is preferably not less than 35mN/mm, more preferably not less than 50 mN/mm, and still more preferablynot less than 75 mN/mm. Preferred composition of the protective layer isdisclosed in Japanese Patent Application No. 8-161645.

The adhesive strength in the invention can be measured according to thefollowing procedure.

When an adhesive tape with sufficient adhesive strength having apredetermined width is adhered onto the protective layer, and thenpeeled at an angle of 90° to the plane of the light sensitiveplanographic printing plate precursor, strength necessary to peel theprotective layer from the photopolymerizable light sensitive layer ismeasured as-the adhesive strength.

The protective layer may further contain a surfactant or a mattingagent. The protective layer is formed, coating on the photopolymerizablelight sensitive layer a coating solution in which the above protectivelayer composition is dissolved in an appropriate coating solvent, anddrying. The main solvent of the coating solution is preferably water oran alcohol solvent such as methanol, ethanol, or iso-propanol.

The thickness of the protective layer is preferably 0.1 to 5.0 μm, andmore preferably 0.5 to 3.0 μm.

(Support)

As the supports used in the invention, an aluminum plate having ahydrophilic surface is used, and the aluminum plate may be a purealuminum plate or an aluminum alloy plate. As the aluminum alloy, therecan be used various ones including an alloy of aluminum and a metal suchas silicon, copper, manganese, magnesium, chromium, zinc, lead, bismuth,nickel, titanium, sodium or iron.

It is preferable that the support in the invention is subjected todegreasing treatment for removing rolling oil prior to surfaceroughening (graining). The degreasing treatments include degreasingtreatment employing solvents such as trichlene and thinner, and anemulsion degreasing treatment employing an emulsion such as kerosene ortriethanol. It is also possible to use an aqueous alkali solution suchas caustic soda for the degreasing treatment. When an aqueous alkalisolution such as caustic soda is used for the degreasing treatment, itis possible to remove soils and an oxidized film which can not beremoved by the above-mentioned degreasing treatment alone. When anaqueous alkali solution such as caustic soda is used for the degreasingtreatment, the resulting support is preferably subjected to desmuttreatment in an aqueous solution of an acid such as phosphoric acid,nitric acid, sulfuric acid, chromic acid, or a mixture thereof, sincesmut is produced on the surface of the support.

As the surface roughening method, an electrolytic surface rougheningmethod is carried out, but prior to the electrolytic surface roughening,a mechanical surface roughening method can be carried out.

Though there is no restriction for the mechanical surface rougheningmethod, a brushing roughening method and a honing roughening method arepreferable. The brushing roughening method is carried out by rubbing thesurface of the support with a rotating brush with a brush hair with adiameter of 0.2 to 0.8 mm, while supplying slurry in which volcanic ashparticles with a particle size of 10 to 100 μm are dispersed in water tothe surface of the support. The honing roughening method is carried outby ejecting obliquely slurry with pressure applied from nozzles to thesurface of the support, the slurry containing volcanic ash particleswith a particle size of 10 to 100 μm dispersed in water. A surfaceroughening can be also carried out by laminating a support surface witha sheet on the surface of which abrading particles with a particle sizeof from 10 to 100 μm was coated at intervals of 100 to 200 μm and at adensity of 2.5×10³ to 10×10³/cm², and applying pressure to the sheet totransfer the roughened pattern of the sheet and roughen the surface ofthe support.

After the support has been roughened mechanically, it is preferablydipped in an acid or an aqueous alkali solution in order to removeabrasives and aluminum dust, etc. which have been embedded in thesurface of the support. Examples of the acid include sulfuric acid,persulfuric acid, hydrofluoric acid, phosphoric acid, nitric acid andhydrochloric acid, and examples of the alkali include sodium hydroxideand potassium hydroxide. Among those mentioned above, an aqueous alkalisolution of for example, sodium hydroxide is preferably used. Thedissolution amount of aluminum in the support surface is preferably 0.5to 5 g/m². After the support has been dipped in the aqueous alkalisolution, it is preferable for the support to be dipped in an acid suchas phosphoric acid, nitric acid, sulfuric acid and chromic acid, or in amixed acid thereof, for neutralization.

In the electrolytic surface roughening method in the invention, theelectrolytically surface roughening is carried out in an acidicelectrolytic solution. The electrolytically surface roughening iscarried out at a current density (in effective value) of from 30 to 100A/dm² for 10 to 120 seconds in a hydrochloric acid or nitric acidelectrolytic solution, the concentration of hydrochloric acid or nitricacid being from 0.4 to 2.8% by weight. The concentration of hydrochloricacid or nitric acid in the hydrochloric acid or nitric acid electrolyticsolution is preferably 1.0 to 2.3% by weight. The current density ispreferably from 30 to 80 A/dm², and more preferably from 40 to 75 A/dm².

There is no limitation to temperature at which the electrolyticallysurface roughening is carried out, the temperature is preferably from 5to 80° C., and more preferably from 10 to 60° C. There is no limitationto voltage applied at which the electrolytically surface roughening iscarried out, the voltage is preferably from 30 to 80 V, and preferablyfrom 40 to 75 V. There is no limitation to quantity of electricity, thequantity of electricity is preferably from 100 to 5000 C/dm², and morepreferably 100 to 2000 C/dm².

It is possible to optionally add, to the electrolytic solution,nitrates, chlorides, amines, aldehydes, phosphoric acid, chromic acid,boric acid, acetic acid or oxalic acid.

After the support has been electrolytically surface roughened, it ispreferably dipped in an acid or an aqueous alkali solution in order toremove aluminum dust, etc. produced in the surface of the support.Examples of the acid include sulfuric acid, persulfuric acid,hydrofluoric acid, phosphoric acid, nitric acid and hydrochloric acid,and examples of the alkali include sodium hydroxide and potassiumhydroxide. Among those mentioned above, the aqueous alkali solution ispreferably used. The dissolution amount of aluminum in the supportsurface is preferably 0.5 to 5 g/m². After the support has been dippedin the aqueous alkali solution, it is preferable for the support to bedipped in an acid such as phosphoric acid, nitric acid, sulfuric acidand chromic acid, or in a mixed acid thereof, for neutralization.

After the surface roughening, anodizing treatment may be carried out.There is no restriction in particular for the method of anodizingtreatment used in the invention, and known methods can be used. Theanodizing treatment forms an anodization film on the surface of thesupport. For the anodizing treatment there is preferably used a methodof applying a current density-of from 1 to 10 A/dm² to an aqueoussolution containing sulfuric acid and/or phosphoric acid in aconcentration of from 10 to 50%, as an electrolytic solution. However,it is also possible to use a method of applying a high current densityto sulfuric acid-as described in U.S. Pat. No. 1,412,768, a method toelectrolytically etching the support in phosphoric acid as described inU.S. Pat. No. 3,511,661, or a method of employing a solution containingtwo or more kinds of chromic acid, oxalic acid, malonic acid, etc. Thecoated amount of the formed anodization film is suitably 1 to 50 mg/dm²,and preferably 10 to 40 mg/dm². The coated amount of the formedanodization film can be obtained from the weight difference between thealuminum plates before and after dissolution of the anodization film.The anodization film of the aluminum plate is dissolved employing forexample, an aqueous phosphoric acid chromic acid solution which isprepared by dissolving 35 ml of 85% by weight phosphoric acid and 20 gof chromium (IV) oxide in 1 liter of water.

It is preferred in the invention that the support after anodizingtreatment is treated in a sodium silicate solution at 20 to 50° C. Thetreatment is carried out preferably at 20 to 50° C., and more preferablyat 20 to 45° C. Temperature less than 20° C. results in lowering of astain elimination property, while temperature exceeding 50° C. resultsin lowering of printing durability. There is no limitation as to asodium silicate concentration in the sodium silicate solution,the-concentration is preferably from 0.01 to 35%, and more preferablyfrom 0.1 to 5%.

It is preferred in the invention that the support after anodizingtreatment is treated in a polyvinyl phosphonic acid solution at 20 to70° C. The treatment is carried out preferably at 20 to 70° C., and morepreferably at 30 to 65° C. Temperature less than 20° C. results inlowering of a stain elimination property, while temperature exceeding70° C. results in lowering of printing durability. There is nolimitation as to a polyvinyl phosphonic acid concentration in thepolyvinyl phosphonic acid solution, the concentration is preferably from0.01 to 35%, and more preferably from 0.1 to 5%.

(Coating)

The prepared coating liquid for the photopolymerizable light sensitivelayer is coated on the support according to a conventional method, anddried to obtain a light sensitive planographic printing plate precursor.Examples of the coating method include an air doctor coating method, ablade. coating method, a wire bar coating method, a knife coatingmethod, a dip coating method, a reverse roll coating method, a gravurecoating method, a cast coating method, a curtain coating method, and anextrusion coating method.

A low drying temperature of the coated photopolymerizable lightsensitive layer cannot provide sufficient printing durability, while tooa high drying temperature of the coated photopolymerizable lightsensitive layer results in marangoni and produces fog at non-imageportions. The drying temperature is-preferably from 60 to 160° C., morepreferably from 80 to 140° C., and still more preferably from 90 to 120°C.

(Image Formation Method)

As a light source for forming an image on the planographic printingplate material in the invention, is used. As the laser, argon laser,He—Ne gas laser, YAG laser or semi-conductor laser is preferably used.In the invention, a laser emitting light having visible wavelengths ispreferably used. Typically, images are preferably formed employing alaser having light with a wavelength regions of from 350 to 450 nm or alaser having light with a wavelength regions of from 470 to 550 nm.

As a laser scanning method by means of a laser beam, there are a methodof scanning on an outer surface of a cylinder, a method of scanning onan inner surface of a cylinder and a method of scanning on a plane. Inthe method of scanning on an outer surface of a cylinder, laser beamexposure is conducted while a drum around which a recording material iswound is rotated, in which main scanning is represented by the rotationof the drum, while sub-scanning is represented by the movement of thelaser beam. In the method of scanning on an inner surface of a cylinder,a recording material is fixed on the inner surface of a drum, a laserbeam is emitted from the inside, and main scanning is carried out in thecircumferential direction by rotating a part of or an entire part of anoptical system, while sub-scanning is carried out in the axial directionby moving straight a part of or an entire part of the optical system inparallel with a shaft of the drum. In the method of scanning on a plane,main scanning by means of a laser beam is carried out through acombination of a polygon mirror, a galvano mirror and an Fθ lens, andsub-scanning is carried out by moving a recording medium. The method ofscanning on an outer surface of a cylinder and the method of scanning onan inner surface of a cylinder are suitable for high density imagerecording, since it is easier to increase accuracy of an optical system.

(Preheating)

In the invention, the exposed planographic printing plate material canbe subjected to heat treatment before or during development. Such a heattreatment can improve adhesion between the support and the lightsensitive photopolymerizable layer, which enhances the effect of theinvention.

Regarding heat treatment, there is, for example, a developing machine inwhich a preheating roller for preheating an exposed planographicprinting plate material to a predetermined temperature is arrangedupstream a development section where the preheating is carried outbefore development. The preheating roller is a roller comprised of apair of rollers, at least one of the pair of the rollers having aheating means within the roller. The roller having a heating means in itis a pipe of a metal with high thermal conductivity such as aluminum oriron, the pipe having a nichrome wire as a heating element. The outsidesurface of the pipe may be covered with a sheet of a plastic such aspolyethylene, polystyrene or Teflon. Details of such a preheating rollercan refer to Japanese Patent O.P.I. Publication No. 64-80962.

In the invention, it is preferred that the preheating is carried out at70 to 180° C. for 3 to 120 seconds.

(Developer)

It is preferred in the invention that the protective layer of an exposedplanographic printing plate material is removed with water prior todevelopment. When the exposed planographic printing plate material isprocessed employing an automatic developing machine, it is preferredthat the exposed planographic printing plate material, after theprotective layer is removed with water before the processing, isprocessed in the automatic developing machine, or that the exposedplanographic printing plate material is processed in an automaticdeveloping machine equipped with a pre-washing tank charged with washingwater upstream the developing tank, the protective layer being removedin the pre-washing tank.

In the invention, the imagewise exposed light sensitive layer, which arecured are at exposed portions, is developed with an alkali developer,whereby the light sensitive layer at non-exposed portions are removed toform an image.

As the alkali developer, a conventional alkali aqueous solution is used.For example, there is an alkali developer containing an inorganic alkaliagent such as sodium silicate, potassium silicate, ammonium silicate,sodium secondary phosphate, potassium secondary phosphate, ammoniumsecondary phosphate; sodium hydrogen carbonate, potassium hydrogencarbonate, ammonium hydrogen carbonate; sodium carbonate, potassiumcarbonate, ammonium carbonate; sodium borate, potassium borate, lithiumborate; sodium hydroxide, potassium hydroxide, and ammonium hydroxide.

The alkali developer can contain organic alkali agents such asmonomethylamine, dimethylamine, trimethylamine, monoethylamine,diethylamine, triethylamine, monoisopropylamine, diisopropylamine,triisopropylamine, n-butylamine, monoethanolamine, diethanolamine,triethanolamine, monoisopropanolamine, diisopropanolamine,ethyleneimine, ethylenediamine, and pyridine.

These alkali agents can be used-singly or as a mixture of two or morethereof. The alkali developer can contain an anionic surfactant, anamphoteric surfactant, or an organic solvent such as alcohol.

EXAMPLES

Next, synthetic example, a method of preparing a support, and exampleswill be explained, but the present invention is not limited thereto. Inthe examples, “parts” represents “parts by weight”, unless otherwisespecified.

Example 1

<<Synthesis of Polymer Binder>>

(Synthesis of Acryl Copolymer 1)

Thirty parts of methacrylic acid, 50 parts of methyl methacrylate, 20parts of ethyl methacrylate, 500 parts of isopropyl alcohol, and 3 partsof α,α′-azobisisobutyro-nitrile were put in a three neck flask undernitrogen atmosphere, and reacted under nitrogen atmosphere for 6 hoursat 80° C. in an oil bath. After that, the reaction mixture was refluxedat a boiling point of isopropyl alcohol for one hour, and 3 parts oftriethylbenzylammonium chloride and 25 parts of glycidyl methacrylatewere further added to the mixture, and reacted for additional 3 hours.Thus, acryl copolymer 1 was obtained. The weight average molecularweight of the acryl copolymer 1 was 35,000, measured according to GPC.The glass transition temperature Tg of the acryl copolymer 1 was 85° C.,measured according to DSC (differential thermal analysis).

(Preparation of Support)

A 0.3 mm thick aluminum plate (material 1050, refining H16) wasdegreased at 60° C. for one minute in a 5% sodium hydroxide solution,washed with water, immersed at 25° C. for one minute in 10% hydrochloricacid solution to neutralize, and then washed with water. The resultingaluminum plate was electrolytically etched using an alternating currentat 25° C. for 60 seconds at a current density of 100 A/dm² in a 0.3weight % nitric acid solution, desmut at 60° C. for 10 seconds in a 5%sodium hydroxide. solution. The desmut aluminum plate was anodized at25° C. for 1 minute at a current density of 10 A/dm² and at a voltage of15 V in a 15% sulfuric acid solution, and further subjected tohydrophilization at 75° C. in a 1% polyvinyl phosphonic acid solution.Thus, support was obtained. The center line average surface roughness(Ra) of the support was 0.65 μm.

<<Preparation of Planographic Printing Plate Material Sample>>

The following photopolymerizable light sensitive layer coating solution1 was coated on the resulting support through a wire bar, and dried at95° C. for 1.5 minutes to give a light sensitive layer having a drythickness of 1.5 gm². Thus, light sensitive planographic printing platematerial sample was obtained.

(Photopolymerizable Light Sensitive Layer Coating Solution 1)

-   Compound having a group capable amount as shown in Table 1 of    undergoing radical polymerization (as shown in Table 1)-   Compound having a group capable amount as shown in Table 1 of    undergoing cationic polymerization (as shown in Table 1)

Photopolymerization initiator amount as shown in Table 1 (as shown inTable 1) Spectral sensitizing dye DR-1 (below) 2.0 parts Acryl copolymer1 40.0 parts N-Phenylglycine benzyl ester 2.0 parts2-Mercaptobenzothiazole 2.0 parts Phthalocyanine pigment 6.0 parts (MHI454 produced by Mikuni Sikisosha) 2-t-Butyl-6-(3-t-butyl-2-hydroxy-5-0.5 parts methylbenzyl)-4-methylphenylacrylate (Sumirizer GS: producedby Sumitomo 3M Co., Ltd.) Decanedioic acid bis- 0.1 parts(2,2,6,6-tetramethyl-piperidin-4-yl) ester (ADK STAB LA-770, produced byAsahi Denka Co., Ltd.) Fluorine-contained surfactant 0.2 parts (F-178K:produced by Dainippon Ink Co., Ltd.) Fluorine-contained surfactant 0.2parts (FC-430: produced by 3M Co., Ltd.) Methyl ethyl ketone 80 partsCyclohexanone 820 parts

The following oxygen shielding layer coating solution 1 was coated onthe photopolymerizable light sensitive layer using an applicator, anddried at 75° C. for 1.5 minutes to give an oxygen shielding layer with adry thickness of 1.8 g/m². Thus, light sensitive planographic printingplate material samples 1 through 11 were prepared.

(Oxygen Shielding Layer Coating Solution 1) Polyvinyl alcohol (GL-05,produced 84.5 parts by Nippon Gosei Kagaku Co., Ltd.) PolyvinylPyrrolidone (K-30, 15.0 parts produced by ISP Japan Co., Ltd.)Surfactant (Surfinol 465, 0.5 parts produced by Nisshin Kagaku KogyoCo., Ltd.) Water 900 parts(Evaluation of Planographic Printing Plate Material Sample)(Sensitivity)

The light sensitive planographic printing plate material sample obtainedabove was imagewise exposed at a resolving degree of 2400 dpi, employinga plate setter (Tiger Cat, produced by ECRM Co., Ltd.) equipped with a532 nm light source). Herein, dpi represents the dot numbers per 2.54cm.

The image pattern used for the exposure comprised a solid image and asquare dot image with a screen number of 175 lpi (lpi means a linenumber per 2.54 cm) and a 50% dot area. Subsequently, the exposed samplewas subjected to development treatment employing a CTP automaticdeveloping machine (PHW 23-V produced by Technigraph Co., Ltd.) toobtain a planographic printing plate. Herein, the developing machinecomprised a pre-heating section for preheating the sample at 110° C. for10 seconds, a pre-washing section for removing the oxygen shieldinglayer before development, a development section charged with developerhaving the following developer composition, a washing section forremoving the developer remaining on the developed sample afterdevelopment, and a gumming section charged with a gumming solution (asolution obtained by diluting GW-3, produced by Mitsubishi Chemical Co.,Ltd., with water by a factor of 2) for protecting the surface of thedeveloped sample. Thus, planographic printing plate sample was obtained.

The lowest exposure energy amount reproducing the solid image above inthe resulting planographic printing plate sample with no reduction ofthe layer thickness at the solid image portions was defined as recordingenergy and evaluated as a measure of sensitivity. The less the recordingenergy is, the higher the sensitivity. The results are shown in Table 1.

<Composition of Developer (Aqueous Solution Containing the FollowingComponents)> Potassium silicate aqueous solution 8.0% by weight NewcolB-13SN (produced by 1.0% by weight Nippon Nyukazai Co., Ltd.) PRONON#204 (produced by 1.0% by weight Nippon Yushi Co., Ltd.) DAPE-0215(produced by 1.0% by weight Nippon Emulsion Co., Ltd.) Potassiumhydroxide amount giving pH 12.3(Printing Durability)

The printing plate material sample obtained above was exposed at anexposure amount of 200 μJ/cm², employing an image with a screen linenumber of 175, and developed with the developer, whereby a printingplate was obtained. Employing the resulting printing plate, printing wascarried out on a press (DAIYA1F-1 produced by Mitsubishi Jukogyo Co.,Ltd.), wherein a coat paper, printing ink (Soybean oil ink, “Naturalith100” produced by Dainippon Ink Kagaku Co., Ltd.), and dampening water(SG-51, H solution produced by Tokyo Ink Co., Ltd., Concentration: 1.5%)were used. The number of prints printed from when printing started untilwhen dot reduction at a highlight portions was produced was defined as ameasure of printing durability.

The results are shown in Table 1. TABLE 1 Compound having a groupcapable Compound having a of undergoing group capable of RecordingSample radical undergoing cationic PhotopolymerizationPhotopolymerization energy Printing No. polymerization polymerizationinitiator 1 initiator 2 (μj/cm²) durability Remarks 1 MR-1: 10 partsExemplified Compound IA-1: 3 parts BR22: 3 parts 20 600,000 Inv. MR-2: 5parts 9: 5 parts MR-3: 10 parts Exemplified Compound 12: 5 parts 2 MR-1:10 parts Exemplified Compound IA-1: 3 parts TZ-4: 3 parts 20 700,000Inv. MR-2: 5 parts 9: 5 parts MR-3: 10 parts Exemplified Compound 12: 5parts 3 MR-1: 10 parts Exemplified Compound IA-7: 3 parts CL49: 3 parts25 550,000 Inv. MR-2: 5 parts 9: 5 parts MR-3: 10 parts ExemplifiedCompound 12: 5 parts 4 MR-1: 10 parts Exemplified Compound IA-7: 3 partsBR50: 3 parts 20 600,000 Inv. MR-2: 5 parts 9: 5 parts MR-3: 10 partsExemplified Compound 12: 5 parts 5 MR-1: 10 parts M101: 10 parts IA-1: 3parts BR22: 3 parts 20 750,000 Inv. MR-2: 5 parts MR-3: 10 parts 6 MR-1:10 parts M201: 10 parts IA-1: 3 parts BR22: 3 parts 20 750,000 Inv.MR-2: 5 parts MR-3: 10 parts 7 MR-1: 10 parts M301: 10 parts IA-1: 3parts BR22: 3 parts 20 700,000 Inv. MR-2: 5 parts MR-3: 10 parts 8 MR-1:10 parts M103: 10 parts IA-1: 3 parts BR22: 3 parts 20 700,000 Inv.MR-2: 5 parts MR-3: 10 parts 9 MR-1: 10 parts None IA-7: 3 parts TZ-4: 3parts 40 400,000 Comp. MR-2: 5 parts MR-3: 10 parts 10 MR-1: 10 partsExemplified Compound IA-7: 3 parts None 300 5,000 Comp. MR-2: 5 parts 9:5 parts MR-3: 10 parts Exemplified Compound 12: 5 parts 11 MR-1: 10parts Exemplified Compound None TZ-4: 3 parts No image — Comp. MR-2: 5parts 9: 5 parts formed MR-3: 10 parts Exemplified Compound 12: 5 partsInv.: Invention,Comp.: ComparativeMR-1: NK OligoU4HA produced by Shinakamura Kagaku Co., Ltd.MR-2: Tetraethylene glycol dimethacrylateMR-3: Reaction product of 1 mol of n-butyl-di(hydroxyethyl)amine, 2 molof tetramethylxylene diisocyanate and 2 mol of2-hydroxy-3-acryloyloxypropyl methacrylate

As is apparent from Table 1 above, the inventive samples provide highsensitivity and high printing durability as compared with comparativesamples.

Example 2

Light sensitive planographic printing plate material samples 21 through31 were prepared in the same manner as in Example 1 above, except thatthe spectral sensitizing dye was changed to DY-2 below, and the compoundhaving a group capable of undergoing radical polymerization, thecompound having a group capable of undergoing cationic polymerization,and the photopolymerization initiator were changed to those as shown inTable 2.

<<Evaluation of Planographic Printing Plate Material Sample>>

The resulting planographic printing plate material samples wereevaluated in the same manner as in Example 1 above, except that thesamples were exposed employing a plate setter (a modified exposuredevice of Tiger Cat, produced by ECRM Co., Ltd.) equipped with a 408 nmlight source with a 30 mW output power), and were exposed at an exposureamount of 200 μJ/cm² for evaluation of printing durability.

The results are shown in Table 2. TABLE 2 Compound having a groupcapable Compound having a of undergoing group capable of RecordingSample radical undergoing cationic PhotopolymerizationPhotopolymerization energy Printing No. polymerization polymerizationinitiator 1 initiator 2 (μj/cm²) durability Remarks 21 MR-1: 10 partsExemplified Compound IA-1: 3 parts BR22: 3 parts 20 400,000 Inv. MR-2: 5parts 9: 5 parts MR-3: 10 parts Exemplified Compound 12: 5 parts 22MR-1: 10 parts Exemplified Compound IA-1: 3 parts TZ-4: 3 parts 15500,000 Inv. MR-2: 5 parts 9: 5 parts MR-3: 10 parts ExemplifiedCompound 12: 5 parts 23 MR-1: 10 parts Exemplified Compound IA-7: 3parts CL49: 3 parts 20 500,000 Inv. MR-2: 5 parts 9: 5 parts MR-3: 10parts Exemplified Compound 12: 5 parts 24 MR-1: 10 parts ExemplifiedCompound IA-7: 3 parts BR50: 3 parts 15 400,000 Inv. MR-2: 5 parts 9: 5parts MR-3: 10 parts Exemplified Compound 12: 5 parts 25 MR-1: 10 partsM101: 10 parts IA-1: 3 parts BR22: 3 parts 10 600,000 Inv. MR-2: 5 partsMR-3: 10 parts 26 MR-1: 10 parts M201: 10 parts IA-1: 3 parts BR22: 3parts 12 500,000 Inv. MR-2: 5 parts MR-3: 10 parts 27 MR-1: 10 partsM301: 10 parts IA-1: 3 parts BR22: 3 parts 10 500,000 Inv. MR-2: 5 partsMR-3: 10 parts 28 MR-1: 10 parts M103: 10 parts IA-1: 3 parts BR22: 3parts 12 500,000 Inv. MR-2: 5 parts MR-3: 10 parts 29 MR-1: 10 partsNone IA-7: 3 parts TZ-4: 3 parts 40 200,000 Comp. MR-2: 5 parts MR-3: 10parts 30 MR-1: 10 parts Exemplified Compound IA-7: 3 parts None 200Z3,000 Comp. MR-2: 5 parts 9: 5 parts MR-3: 10 parts Exemplified Compound12: 5 parts 31 MR-1: 10 parts Exemplified Compound None TZ-4: 3 parts Noimage — Comp. MR-2: 5 parts 9: 5 parts formed MR-3: 10 parts ExemplifiedCompound 12: 5 partsInv.: Invention,Comp.: Comparative

As is apparent from Table 2 above, the inventive samples provide highsensitivity and high printing durability as compared with comparativesamples.

EFFECT OF THE INVENTION

The present invention can provide a light sensitive composition, a lightsensitive planographic printing plate material, and a manufacturingmethod of a printing plate providing high sensitivity and excellentprinting durability.

1. A light sensitive composition containing a compound A having a groupcapable of undergoing radical polymerization, a compound B having agroup capable of undergoing cationic polymerization, aphotopolymerization initiator C, and a polymer binder D, wherein thephotopolymerization initiator C comprises an iron-arene complex and ahalogenated alkyl group-containing compound.
 2. The light sensitivecomposition of claim 1, wherein the halogenated alkyl group-containingcompound is at least one selected from the group consisting of atrichloromethyl group-containing compound, a tribromomethylgroup-containing compound, a dichloromethyl group-containing compound,and a dibromomethyl group-containing compound.
 3. The light sensitivecomposition of claim 1, wherein the compound B having the group capableof undergoing cationic polymerization further has a group capable ofundergoing radical polymerization, the group capable of undergoingcationic polymerization comprising any one of an oxirane ring, anoxetane ring and a dioxolane ring in the chemical structure.
 4. Thelight sensitive composition of claim 1, wherein the compound B is acompound represented by the following formula (A):

wherein R¹ represents a hydrogen atom, or a methyl group; R² representsan alkyl group; and X¹ represents a single bond or a divalent organicgroup.
 5. The light sensitive composition of claim 1, wherein thecompound B is at least one selected from the group consisting of acompound represented by the following formula (B) and a compoundrepresented by the following formula (C):

wherein R³ represents a substituted or unsubstituted alkyl group, asubstituted or unsubstituted,aryl group or a substituted orunsubstituted acyl group; R⁴ represents a hydrogen atom or an alkylgroup; and X² represents a single bond or a divalent organic group,

wherein R⁵ represents a substituted or unsubstituted alkyl group or asubstituted or unsubstituted aryl group; R⁶ represents a hydrogen atomor an alkyl group; and X³ represents a single bond or a divalent organicgroup.
 6. A light sensitive planographic printing plate materialcomprising a support having a hydrophilic surface, and coated on thehydrophilic surface, the light sensitive composition of claim
 1. 7. Aprocess of manufacturing a planographic printing plate, the processcomprising the step of: imagewise exposing the light sensitiveplanographic printing plate material of claim 6, employing a laseremitting light with a wavelength of from 350 to 450 nm to record animage.
 8. A process of manufacturing a planographic printing plate, theprocess comprising the step of: imagewise exposing the light sensitiveplanographic printing plate material of claim 7, employing a laseremitting light with a wavelength of from 470 to 550 nm to record animage.